Control system for an automotive automatic power transmission

ABSTRACT

A control system for controlling the line pressure in a hydraulic control system of an automotive automatic power transmission, in which a line pressure regulator valve is controlled by a variable back pressure produced by a fluid jet nozzle which is electrically controlled in response to a variation in the vehicle speed, whereby a cutback is rapidly effected in the line pressure to effect a smooth shifting between the gear ratios.

United States Patent Irie et al.

451 Oct. 3, 1972 CONTROL SYSTEM FOR AN AUTOMOTIVE AUTOMATIC POWERTRANSMISSION [72] Inventors: Namio Irie, Yokohama; Ichimura Hirohisa,Yokohama, both of Japan [73] Assignee: Nissan Motor Company, Limited,Yokohama, JapaiT" [22] Filed: Oct. 13, 1970 [21] Appl. No.: 80,310

[30] Foreign Application Priority Data Oct. 13, 1969 Japan ..44/81384521 US. Cl. ..74/864 [51] Int. Cl. ..B60k 21/00 [58] Field of Search..74/863, 864, 866-869 [56] References Cited UNITED STATES PATENTS3,505,909 4/1970 Maurice ..74/864 3/1971 Shirai et a1 ..74/866 PrimaryExaminer-C. J. Husar AttorneyMcCarthy, Depaoli, OBrien and Price [57]ABSTRACT A control system for controlling the line pressure in ahydraulic control system of an automotive automatic power transmission,in which a line pressure regulator valve is controlled by a variableback pressure produced by a fluid jet nozzle which is electricallycontrolled in response to a variation in the vehicle speed, whereby acutback is rapidly effected in the line pressure to effect a smoothshifting between the gear ratios.

6 Claims, 6 Drawing Figures PATENTED I973 3,695,122

SHEET 2 or 4 INVENTORS A ORNEYS m w 5 H w 0 MR NH Y a m CUTBACK POINTTURBINE SPEED (VEHICLE SPEED) TURBINE SPEED (VEHICLE SPEED) INVENTORSNAM/0 IRIE HlROH/SA ICHIMURA "/11. (n/ Z 10 .05 mm ATTORNEYS mDOKOPmZGZm PATENTEnnma m2 SHEET '4 OF 4 INVENTORS NAM/o IRIE BY H/ROHISA'ICHIMURA CONTROL SYSTEM FOR AN AUTOMOTIVE AUTOMATIC POWER TRANSMISSIONThis invention relates to an automotive power transmission, and moreparticularly to a control system for the automotive automatic powertransmission.

An automatic power transmission used in a motor vehicle commonlyincludes a hydraulic control system for controlling the frictionelements, such as friction clutches and brakes, to selectively provide aplurality of gear ratios. To effect smooth shifting between the gearratios, it is desirable to change a torque capacity of the frictionelements in accordance with the variations in engine load and vehiclespeed. The required torque capacity increases as the engine loadincreases so that it must be relatively great at starting or during lowspeed driving and relatively small during high speed.

If the torque capacity of such friction element is too small as comparedto the required torque capacity at a given time, the slippage betweenthe members to be coupled to each other will be too high, resulting inan inaccurate operation or runaway of the engine will take place. If, incontrast, the torque capacity of the friction element is too large, theclutch or brake will engage instaneously and thus an objectionable shockwill take place. Since the torque capacity of the friction elementdepends on the level of a line pressure used in the hydraulic controlsystem, smooth engagement of the friction elements can be accomplishedby controlling the line pressure so as to minimize the differencebetween the torque capacity of the friction element and the requiredtorque to be transmitted.

In the conventional hydraulic control system, the cutback of the linepressure is effected by hydraulically producing a cutback signal by theuse of a certain suitable means, such as hydraulic shift valves. Theseshift valves, however, are not fully acceptable because of their limitedresponsiveness and inability of effecting a smooth shifting between thegear ratios particularly where the power transmission is controlledelectronically.

It is, therefore, an object of the invention to provide an improvedcontrol system for rapidly effecting a cutback of a line pressure tominimize the shock or jerk of friction elements to be engaged, wherebythe shifting between the gear ratios is effected smoothly.

It is another object of the invention to provide a control systemadapted to electronically produce a cutback of the line pressure wherebythe shifting of the gear ratios is effected quickly and precisely.

In the accompanying drawings: I

FIG. 1 is a graphical representation showing the variation of the outputtorque against the turbine speed of a torque converter used in a commonautomatic power transmission;

FIG. 2 is a schematic view of a control system embodying the invention;

FIG. 3 is a diagram illustrating an example of the electric controlcircuit used in the control system of FIG. 2;

FIG. 4 is a graphical representation of a cutback range which isachieved where the control system of FIGS. 2 and 3 is used;

FIG. 5 is a schematic view illustrating an example of a hydrauliccontrol circuit forming part of the control system of FIG. 2; and

FIG. 6 is a graphical representation of the line pressures which areobtainable in accordance with the invention.

As illustrated in FIG. 1, the output torque of the torque convertervaries in accordance with the turbine speed thereof. The curve Aindicates the output torque of the torque converter at higher enginetorque and the curve B the output torque of the torque converter atlower engine torque, wherein C and C indicate the respective couplingpoints of the torque converter. In order to achieve smooth engagement ofthe friction elements, it is preferable to control the line pressuresubstantially in proportion to the output torque of the torqueconverter. In accordance with the invention, a cutback signal iselectronically produced in response to a variation in the turbine speedor in the vehicle speed. The cutback signal is then applied to theregulator valve of the hydraulic control system for effecting a cutbackin the line pressure thereby to achieve smooth shifting between the gearratios.

A control system embodying the invention is schematically illustrated inFIG. 2, the system being shown as incorporated in a common automaticpower transmission which is generally represented by reference numeral10. The power transmission 10 has, as is customary, a drive shaft (notshown) which is connected to and driven by a suitable prime mover suchas an internal combustion engine 11, and a driven shaft 12 which isconnected by suitable means to driving wheels (not shown) of the motorvehicle.

A control system generally indicated by reference numeral 13 includes avehicle speed sensor 14 for electronically detecting the vehicle speedor the revolution of the driven shaft 12 to generate a voltage signalcorresponding thereto. The vehicle speed sensor 14 may be of anysuitable electronic type having a negative voltage output whichincreases as the vehicle speed decreases. The voltage signal generatedby the vehicle speed sensor 14 is applied through a line 15 to anelectronic control circuit 16 where it is utilized for electronicallyproducing a cutback signal. Connected to the electronic control circuit16 is an engine torque sensor 17 which detects an output torque of theengine 11 for generating a voltage signal corresponding thereto. Theengine torque sensor 17 may be of any suitable electronic type having anegative voltage output which increases as the engine torque increases.The engine torque may be determined by detecting an intake manifoldvacuum or an accelerator pedal position. The voltage signal produced bythe engine torque sensor 17 is also fed to the electronic controlcircuit 16 through a line 18. The electronic control circuit 16 isresponsive to both the vehicle speed signal and engine torque signal andgenerates a cutback signal which is applied through a line 19 to anelectronic actuator 20. In response to the cutback signal the electronicactuator 20 effects a cutback of a line pressure of the hydrauliccontrol circuit 20. Thus, the hydraulic control circuit 20 controls theautomatic power transmission 10 so as to achieve smooth engagementbetween the gear ratios.

FIG. 3 shows an example of the electronic-control circuit 16 whichcomprises a Schmidt trigger circuit. As shown, a voltage signal Vdelivered from the vehicle speed sensor 14 through the line 15 isapplied through a resistor 22 to a junction 23 while voltage signal V,

transmitted from the engine torque sensor 17 through the line 18 is alsoapplied to the junction 23 through a resistor 24. The voltage signal Vincreases as the vehicle speed decreases while the voltage signal V,increases as the engine torque increases. The junction 23 is connectedthrough a line 25 to the base of a transistor 26. The collector of thetransistor 26 is connected through a resistor 27 to a power supply line28 supplying a constant voltage of, for instance, l volts. The emitterof the transistor 26 is grounded. A diode 29 is connected between theemitter and the base of the transistor 26 to prevent a flow of anexcessive voltage across the transistor. The collector of the transistor26 is also connected through a resistor 30 to the base of a transistor31. The base of the transistor 31 is grounded through a resistor 32. Thecollector of the transistor 31 is connected to the line 28 through aresistor 33 and the emitter thereof is grounded. The collector of thetransistor 31 is connected through a resistor 34 to the line 25 and alsoto the base of a transistor 35. The transistor 35 has its collectorconnected to the line 28 through a resistor 36 and its emitter connectedto a transistor 37. The collector of the transistor 37 is connectedthrough a resistor 38 to the line 28, and the emitter thereof isconnected to the base of a transistor 39. The collector of thetransistor 39 is connected to the line 28 through a diode 40 whichprevents a flow of an excessive voltage across the transistor 39. Ajunction 41 intervening between the diode 40 and the collector of thetransistor 39 is connected to a line 42. The lines 28 and 42 areconnected to lines 28a and 42a leading to a coil (not shown) of theelectronic actuator 20.

When the voltage applied to the junction 23 exceeds a predeterminedvalue, the transistor 26 becomes conductive, whereby the transistors 31,35, 37 and39 are also made conductive. Thus, the current passes from theelectric power source to the lines 28a and 42a, leading to the coil ofthe electronic actuator 20, thereby operating the electronic actuator20. When, on the other hand, the voltage applied to the junction 23falls below a predetermined value, the transistor 26 and accordingly thetransistors 31, 35, 37 and 39 are made nonconductive, causing theelectronic actuator 20 to become inoperative. It will be noted that thevoltage appearing at the junction 23 increases as the turbine speeddecreases or as the engine torque increases.

FIG. 4 illustrates an example of the range in which the electronicactuator 20 is held at rest. This range is referred to as the cutbackrange hereinafter.

Referring next to FIG. 5, there is is shown the hydraulic controlcircuit 20 in detail which is controlled by the electronic controlcircuit 16 so as to effeet the cutback of the line pressure. As shown,the hydraulic control circuit 21 includes an oil pump 50, a linepressure regulator valve 51, an amplifier valve 52, a throttle valve 53,and fluid jet nozzle 54 which is adapted to be controlled by theelectronic actuator 20.

The oil pump 50, which may be of any suitable construction, supplied apressurized fluid through a sump 55, which pressurized fluid is passedto a line pressure conduit 56. The line pressure 56 is connected to theline pressure regulator valve 51 which in turn is connected through abranch conduit 56a to control or servo devices, not shown, for actuatingthe friction clutches and brakes to effect shifting between-the gearratios in the power transmission.

The line pressure regulator valve 51 regulates the pressure in the linepressure conduit 56 and includes a slidable valve spool 57 having aplurality of spaced lands 58, 59, 60 and 61. The regulator valve 51 hasports 62, 63, 64, 65, 66 and 67. The port 62 communicates with the fluidjet nozzle 54. The port 63, which has an orifice 63a thereimcommunicateswith the line pressure conduit 56, with which the ports 64 and 65 alsocommunicate. The port 67 is a drain port through which the excess fluidin the line pressure conduit 56 is drained off to reduce the linepressure. A spring 68 is provided for moving the valve spool 57 upwardlyof the drawing. As shown, the regulator valve 51 is operativelyconnected to the amplifier valve 52.

The amplifier valve 52 includes a slidable valve spool 69 having spacedlands 70 and 71. On the valve spool 69 is mounted a push rod 72 whichcooperates with the land 61 of the regulator valve 51 to increase theline pressure in the line pressure conduit 56. The valve spool 69 isslidably disposed in a sleeve 73 which has a port 74 communicating witha branch conduit 75a of a conduit 75 which in turn communicates with thethrottle valve 53.

The throttle valve 53 includes a slidable valve spool 76 having a bore77 therein. The throttle valve 53 has a plurality of ports 78, 79 and80. The port 78 is a drain port. The port 79 communicates with theconduit 75 while the port 80 communicates with a branch conduit 56bcommunicating with the branch conduit 56a. The valve spool 76 has spacedlands 81 and 82. On the land 82 is mounted a push rod 83 of a throttlemodulator valve 84 which communicates with the intake manifold (notshown) of the engine. The throttle modulator valve 84 operates inaccordance with the variation in the intake manifold vacuum of theengine so that the push rod 83 moves toward the valve land 82. Thus, thepush rod 83 biases the valve spool 76 downwardly of the drawing.

On the other hand, the fluid pressure in the port 79 is drawn into thefluid chamber (not numbered) of the throttle valve 53 and thus acts onthe lower end of the valve land 81. By this action, the fluid pressureis modulated to a value that is determined by the force acting on thevalve land 82. Consequently, the fluid pressure in the conduit 75 riseswhen the throttle valve is fully opened and falls when the throttlevalve is slightly opened, that. is, when the intake manifold vacuum isrelatively high. Thus, the fluid pressure in the port 79 responds to theintake manifold vacuum of the engine, and is utilized for varying theline pressure. This fluid pressure is referred to as a throttle pressurehereinafter.

The throttle pressure in the conduit 75 is distributed to the port 74 ofthe amplifier valve 52 and acts on the land 71 to move the valve spool69 upwardly of the drawing. This causes the valve spool 57 of theregulator valve 51 to move upwardly, thereby blocking the communicationbetween the ports 64 and 66 and the communication between the ports 65and 67. Thus, the line pressure is increased in the line pressureconduit 56. As the intake manifold vacuum increases, the line pressurein the regulator valve 51 is increased accordingly. The torque capacityrequired of the friction elements is established. It will thus beunderstood that, as the throttle pressure decreases, the line pressuredecreases.

In order to change the torque capacity of the friction elements, it isnecessary to effect a cutback of the line pressure as the vehicle speedincreases, as previously discussed above. This is because of the factthat the torque converter operates at a reduced torque ratio as thevehicle speed increases. When the vehicle speed is increased, it isdesired that the torque delivered from the torque converter be reducedsince the torque ratio itself is decreased then. A desired cutback ofthe line pressure is effected through operation of the fluid jet nozzle54.

The fluid jet nozzle 54 communicates with a fluid chamber 86 to whichthe throttle pressure is distributed through an orifice 85 provided inthe branch conduit 75b. The sectional area of the nozzle 54 is greaterthan that of the orifice 85, so that the fluid pressure in the fluidchamber 86 is higher than the throttle pressurein the conduit 75. Thefluid jet nozzle 54 cooperates with the electronic actuator 20.

The electronic actuator is herein shown to be constructed as a solenoiddevice comprising a solenoid coil 87, a combination armature and plunger88 and a spring 89 for biasing the plunger 88 to protrude. Theelectronic actuator 20 is so arranged that the plunger 88 protrudes toclose the fluid jet nozzle 54 when the vehicle is driven at a moderatespeed. At this instant, the electronic actuator 20 is held inoperative,so that the power loss is saved considerably.

When, in operation, the electronic actuator 20 is energized, then theplunger 88 is retracted so that the nozzle 54 is opened. The fluidobtainingin the fluid 'chamber 86 is then discharged through the nozzle54.

Consequently, the fluid pressure in the branch conduit 75c yields to theforce of the spring 68 of the regulator valve 51. In this instance, thethrottle pressure is passed to the port 74 of the amplifier valve 52.The throttle pressure then acts on the land 71 to move the push rod 72upwardly. This causes the valve spool 57 to move upwardly, therebyinterrupting the communications between the ports 64 and 66 and betweenthe ports 65 and 67. Thus, the line pressure rises in the line pressureconduit 56 when the vehicle is driven at a relatively low speed.

When, now, the electronic actuator 20 is de-energized, then theplunger.88 protrudes into closing contact with the nozzle 54. The nozzle54 being closed, a back pressure is built up in the fluid chamber86. Theback pressure is passed through the branch conduit 750 to the port 62and thus acts on the land 58 of the regulator valve 51. This causes thevalve spool 57 to move downwardly against the force of the spring 68,with the result that the communications between the ports 64 and 66 andbetween the ports 65 and 67 are established. The fluids in the linepressure conduit 56 are now drained off from the drain ports 66 and 67.The cutback is thus effected in the line pressure and hence the linepressure applied to the friction elements is decreased. The frictionelements are then actuated softly at higher vehicle speeds and anundesirable shock is prevented.

In FIG. 6 there is illustrated the variation in the line pressure whichis obtained as a result of the action of the electronic actuator and thefluid jet nozzle. In FIG.

6, curves D, E and F indicate the line pressure at high, intermediateand low engine torque, respectively. As shown, the larger than enginetorque, the greater is the movement of the cutback point toward thehigher turbine speed, whereby a desired cutback is effected in the linepressure. When the engine torque is at minimum, the throttle pressure isclose to zero, so that there is established no cutback. For this reasonthe variation in the line pressure is represented by a straight line.

It will be apparent from the foregoing that, in accordance with theinvention, a cutback signal is produced electronically so that asatisfactory responsiveness is obtained.

Since, moreover, the electronic actuator is of the type that the plunger88 is retracted when energized, there is no need to supply an electriccurrent to the actuator in the cutback range shown in FIG. 4, so thatthe power loss is minimized under normal driving conditions of thevehicle.

It should also be understood that the same results can be obtained byutilizing a voltage signal developed in accordance with the vehiclespeed instead of turbine speed of the torque converter.

What is claimed is:

1. A control system for controlling a line pressure in a hydrauliccontrol system for an automatic power transmission of a motor vehicledriven by an internal combustion engine, comprising, in combination, aline pressure regulator valve provided in said hydraulic control systemfor regulating the line pressure therein, a fluid jet nozzle connectedto said regulator valve, a first sensing means operatively connected tothe driven shaft of said transmission to sense vehicle speed forgenerating a first voltage signal corresponding thereto, a secondsensing means operatively connected to the intake manifold of the engineto sense an output torque of the engine for generating a second voltagesignal corresponding thereto, an electronic control circuit electricallyconnected to said first and second sensing means for producing a cutbacksignal in response to said first and second voltage signals, and anelectronic actuating means electrically connected to said electroniccontrol circuit and having a movable member movable toward and away fromsaid fluid jet nozzle, said electronic actuating means being responsiveto said cutback signal to cause said movable member to close said fluidjet nozzle for thereby producing a back pressure to effect a cutback insaid line pressure through said regulator valve.

2. A control system according to claim 1, wherein said first voltagesignal increases as the vehicle speed decreases and wherein said secondsignal increases as the engine torque decreases.

3. A control system according to claim 2, wherein said cutback signal isproduced when said first and second voltage signals become lower than apredetermined value.

4. A control system according to claim 1, wherein said line pressureregulator valve is connected to a throttle valve producing a throttlepressure in relation to the output torque of the engine, said throttlepressure being applied to said line pressure regulator valve to effect acutback in line pressure.

5. A control system according to claim 1, wherein said electronicactuating means is controlled in response to the vehicle speed andengine torque to raise a cutback point to a higher level as the enginetorque increases.

6. A control system according to claim 1, wherein said electroniccontrol circuit comprises 21 Schmidt trigger circuit including aplurality of transistors, resistors and diodes adapted to effect ON andOFF operations for generating a cutback signal.

1. A control system for controlling a line pressure in a hydrauliccontrol system for an automatic power transmission of a motor vehicledriven by an internal combustion engine, comprising, in combination, aline pressure regulator valve provided in said hydraulic control systemfor regulating the line pressure therein, a fluid jet nozzle connectedto said regulator valve, a first sensing means operatively connected tothe driven shaft of said transmission to sense vehicle speed forgenerating a first voltage signal corresponding thereto, a secondsensing means operatively connected to the intake manifold of the engineto sense an output torque of the engine for generating a second voltagesignal corresponding thereto, an electronic control circuit electricallyconnected to said first and second sEnsing means for producing a cutbacksignal in response to said first and second voltage signals, and anelectronic actuating means electrically connected to said electroniccontrol circuit and having a movable member movable toward and away fromsaid fluid jet nozzle, said electronic actuating means being responsiveto said cutback signal to cause said movable member to close said fluidjet nozzle for thereby producing a back pressure to effect a cutback insaid line pressure through said regulator valve.
 2. A control systemaccording to claim 1, wherein said first voltage signal increases as thevehicle speed decreases and wherein said second signal increases as theengine torque decreases.
 2. A control system according to claim 1,wherein said first voltage signal increases as the vehicle speeddecreases and wherein said second signal increases as the engine torquedecreases.
 3. A control system according to claim 2, wherein saidcutback signal is produced when said first and second voltage signalsbecome lower than a predetermined value.
 4. A control system accordingto claim 1, wherein said line pressure regulator valve is connected to athrottle valve producing a throttle pressure in relation to the outputtorque of the engine, said throttle pressure being applied to said linepressure regulator valve to effect a cutback in line pressure.
 5. Acontrol system according to claim 1, wherein said electronic actuatingmeans is controlled in response to the vehicle speed and engine torqueto raise a cutback point to a higher level as the engine torqueincreases.
 6. A control system according to claim 1, wherein saidelectronic control circuit comprises a Schmidt trigger circuit includinga plurality of transistors, resistors and diodes adapted to effect''''ON'''' and ''''OFF'''' operations for generating a cutback signal.